1. Field of the Invention
The present invention relates to network repeaters, more specifically to units incorporating two or more IEEE 802.3 compliant repeaters each operating at different data rates. The principle of monitoring link integrity and adjusting operating speed to minimize error rate may also be applied to other networking equipment, including Bridges, Routers, Network interfaces and switches.
2. Background Art
Network repeaters are typically used to connect between network nodes, for example network stations serving as data terminal equipment (DTE) on different network media. Repeaters provide the advantage of extending the physical distance between network nodes by receiving a data packet from one network medium, reconditioning the physical signal, and outputting the data packet to a second network medium. The repeater may also forward carrier sense and collision signals, effectively extending the collision domain of one medium onto the second medium.
Repeaters interconnecting network nodes on different network media have conventionally been configured to connect only networks operating at the same transmission rate. One problem encountered in higher-speed networks, for example 100 Mb/s IEEE 802.3 networks, is the identification of a link, between the network repeater and a remote network node on one of the network repeater ports, having a poor level of integrity. In particular, there is a need to discover links between a repeater port and a network node that are not performing up to specifications, for example due to a poor cable connection or condition, a faulty network interface device at the remote node, etc.
One proposal for handling link failure is by using network management capabilities, for example, a remote management function (i.e., network manager) configured for monitoring and controlling operations of the repeater and the network nodes. For example, a remote management technique may use a management protocol to transmit management information between the repeater and the network manager. However, such an arrangement necessarily relies on a management function, and hence is inapplicable in unmanaged network. Moreover, the monitoring of links by a centralized network manager requires that each unit to be managed must incorporate a function to handle the management protocol (an agent), thereby increasing the complexity and processing requirements of the managed unit, e.g., a repeater.
There is a need for an arrangement for interconnection of different speed network nodes using a repeaters, where the link integrity between a repeater and the network nodes can be reliably monitored without the necessity of a network manager.
There is also a need for an arrangement in a network having a repeater for monitoring the link status of high speed data links, and automatically changing a selected high speed data link to a slower data rate based on detection of a marginal or unacceptable link status on the selected high speed data link.
There is also a need for an arrangement in a network repeater for monitoring the link status of high speed data links, where the error rate of a link can be reliably determined despite the presence of transient errors that may otherwise create the perception of an artificially high error rate.
These and other needs are obtained by the present invention, where a network repeater monitors each repeater port link in communication with a remote network node at a corresponding data rate. The network repeater monitors each link by counting in a first counter a detected number of symbol errors within a first interval. A second counter may also be used for increased accuracy in detecting a symbol error rate. In such cases, the second counter is incremented if the detected number of symbol errors exceeds a first threshold within the first interval. If the second counter reaches a second threshold within a second interval, substantially longer than the first interval, then the link integrity is deemed to have an unacceptably high error.
According to one aspect of the present invention, a method in a network repeater includes establishing a link with a remote network node at a prescribed rate via a network medium, and determining an integrity of the link. The integrity of the link is determined by counting in a first counter a detected number of symbol errors within a first interval, incrementing a second counter if the detected number of symbol errors exceeds a first threshold within the first interval, and determining if the second counter reaches a second threshold within a second interval including a successive plurality of the first intervals, the link integrity based on the second counter reaching the second threshold within the second interval. Use of the first and second counters enables the monitoring of symbol errors to be more evenly distributed, minimizing the possibility of transient symbol errors generating an artificially high symbol error rate.
An additional feature of this aspect includes selectively reducing the data rate on the network medium to a reduced data rate in response to the number of symbol errors exceeding prescribed threshold. Hence the network repeater, upon detecting that the number of symbol errors exceeds the prescribed threshold, may reduce the data rate on the identified link in an effort to provide a more reliable link that has a reduced number of symbol errors occurring relative to the link having the higher data rate.
Another aspect of the present invention provides a network repeater having a plurality of repeater ports, configured for sending and receiving data packets between remote nodes via respective network media. The network repeater includes a first repeater core configured for sending and receiving data packets between a first group of the repeater ports according to a first data rate, and a second repeater core configured for sending and receiving data packets between a second group of the repeater ports according to a second data rate slower than the first data rate. An auto-negotiation unit is configured for selecting one of the first and second data rates for establishment of links between the repeater ports and the respective remote nodes via the respective network media. A symbol error detector is configured for detecting a number of symbol errors on at least one of the links operating at the first data rate. The symbol error detector includes a first counter for counting a detected number of symbol errors within a first interval, and a second counter for counting, within a second interval larger than the first interval, a number of the first intervals having the detected number of symbol errors exceeding a first prescribed threshold. A controller detects an integrity of at least the one link based on the counter value of the second counter reaching a second threshold within the second interval. The symbol error detector can detect the number of symbol errors on at least one link, enabling monitoring of each link without the necessity of an external management function. Moreover, the use of the first and second counters ensures that the symbol error detector does not erroneously determine a poor link integrity merely due to a presence of transient errors within one or two of the first detection intervals. The controller thus enables the link to be reduced to a lower speed in the event that a higher number of symbol errors are detected over a plurality of the first intervals, indicating a higher incidence of symbol errors over a greater distribution.
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.